QT Dispersion in Single-Vessel Coronary Artery Disease: Is There Relation Between QT Dispersion and the Diseased Coronary Artery or Lesion Localization?

lt has been shown that QT dispersion (QTD) increases during episodes of myocardial ischemia or infarction. However, no extensive data on the relation between the diseased coronary artery or the localization of stenosis and the QTD are available. The aim of this study was to examine the relation between QTD and the coronary artery involved and lesion localization during exercise stress test (EST) in patients with single-vessel coronary artery disease (CAD) without prior myocardial infarction. We studied 53 patients with normal coronary artery and 119 patients with single-vessel CAD. All patients underwent EST first and then coronary angiography with the suspicion of CAD. QT interval parameters were measured at rest and at the 2nd minute of the recovery period (Rec-2) in all patients. Corrected QT dispersion (QTcD) at rest was found higher in all single-vessel disease groups [left anterior descending artery (LAD), circumflex artery (CX), right coronary artery (RCA)] compared to control group (QTcD at rest was 33±12 ms in the control group, 49±13 ms in LAD group, 45±10 ms in the CX group and 44±11 in the RCA group, p<0.05). QTcD at rec-2 period was also markedly higher in LAD, CX and RCA groups compared to the control group (38±12 ms in the control group, 68±18 ms in LAD group, 59 ±17 ms in the CX group and 61±18 ms in the RCA group, p<0.005). No relation was found between QT dispersion and the diseased coronary artery or lesion localization. Furthermore, it was observed that QTD increase is well correlated with ST segment depression during post-exercise period (r=0.706, p>0.001). In conclusion, no quantitative difference was found in QT dispersion according to the diseased coronary artery and proximal or distal lesion localization. However, it was observed that patients with singlevessel CAD had wider baseline QT dispersion when compared to control group which further increased significantly with exercise. Our findings support the opinion that severity of localized ischemia rather than the extent of CAD would be expected to have greater effect on inducible QT dispersion.